Crater great to visit, but don't linger

Nothing is more beautiful than Kilauea caldera on a clear, crisp day. Steam escapes from a few spots inside and outside, and koa`e kea birds ride the thermals over the caldera floor. What could possibly be of concern in this mythical, but also real-life location on such a day? It depends on exactly where you might be going in the caldera.

Recently, an HVO staff member experienced slight nausea, drowsiness, and headaches when repairing some equipment in an underground vault just off the edge of Halema`uma`u crater. A quick investigation revealed that carbon dioxide gas concentrations were especially high in the vault.

Scientists have known for a long time that carbon dioxide bubbles out of magma deep beneath the floor of volcanoes like Kilauea – thousands of tons each day. Humans produce carbon dioxide when we exhale and we even consume it in soda, beer, and champagne. What’s the big deal?

Carbon dioxide (CO2) is a colorless, nearly odorless gas that is denser than air. While toxic at very high concentrations, it can kill at lower concentrations by displacing oxygen, causing asphyxiation. CO2 makes up less than 1 percent of the air we normally breathe in and about 4.5 percent of each breath we exhale. Breathing air that is more than 7 percent CO2 can produce unconsciousness in just a few minutes.

Usually the large amounts of carbon dioxide released by Kilauea get dispersed by winds so we can breathe nice, healthy, oxygen-rich air on the caldera floor. Because CO2 is heavier than air, it doesn’t readily rise into the atmosphere and, instead, tends to pool in low areas. In the summit caldera these areas include underground openings, such as lava tubes, pits, and underground vaults. In such places, simple filter masks cannot protect individuals from asphyxiation.

Carbon dioxide emitted from other volcanoes has killed people. In 1998, a cross-country skier died in a snow pit at Mammoth Mountain, California. Lethal concentrations were found in that pit and several other locations including a campground which was subsequently closed. This area is within Long Valley caldera and is monitored by the USGS’s Long Valley Volcano Observatory.

Another volcano-related carbon dioxide disaster occurred during the 1979 eruption on the Dieng Plateau, Indonesia. A cloud of gas released during the eruption claimed over 140 lives of people trying to escape and later more lives amongst would-be rescuers.

Better known but less related to active volcanism was the overturn of Lake Nyos in Cameroon, West Africa. Several lakes in this region are nestled in old volcanic craters. In these lakes, carbon dioxide from cold springs built up in the deepest lake waters. In 1986, gas suddenly bubbled out (possibly initiated by a landslide into the lake), flowed downhill, and asphyxiated about 1,700 people.

So what’s causing the high CO2 levels in Kilauea caldera? The latest measurements inside the instrument vault at Halema`uma`u showed concentrations around 8 percent – enough to cause loss of consciousness with prolonged exposure. Lack of strong trade winds could allow more gas to pool than normal, but there haven’t been long periods of unusually weak winds lately.

HVO scientists noted an increase in sulfur dioxide release from the summit caldera that began near the end of March and has almost doubled so far. This increase followed a prolonged surge in eruptive activity–both gas and lava–at the east rift eruption site. Overall CO2 emissions from Kilauea appear to have increased, as well.

Regardless of the cause, there is an invisible and virtually undetectable hazard to those that venture into low spots in the caldera floor. Nevertheless, those of us who visit the Halema`uma`u area would do well to follow the example of the koa`e kea birds and keep a respectful distance from these low-lying areas.

Activity Update

Eruptive activity at Pu`u `O`o continues. On clear nights, glow is visible from several vents within the crater and on the southwest side of the cone.

The PKK lava tube continues to produce intermittent surface flows from above the top of Pulama pali to the ocean. Three ocean entries were active as of June 2. The largest is at East Lae`apuki with two smaller entries at Kamoamoa and East Kamoamoa. Surface flows are intermittently active inland of the entries. The East Lae`apuki entry is the closest activity to the end of Chain of Craters Road, in Hawai`i Volcanoes National Park, and is located about 4.5 km (3 miles) from the ranger shed. Expect a 2-hour walk each way and bring lots of water.

Stay well back from the sea cliff, regardless of whether there is an active ocean entry or not. Remember—the beaches that sometimes form next to an active bench are just as dangerous as the bench itself. Stay off both, and heed the National Park warning signs.

During the week ending June 1, one earthquake was reported felt on Hawai`i Island. A magnitude-2.9 quake occurred 8 km (5 miles) southeast of Waimea at a depth of 15 km (9 miles) at 2:38 p.m. on Wednesday, June 1; this earthquake was felt at Pa`auilo, Waikoloa, and Waimea.

Mauna Loa is not erupting. During the week ending June 1, six earthquakes were recorded beneath the summit area. Two were deep and long-period in nature. Inflation continues, but at a slightly reduced rate over the last few weeks.

This article was written by scientists at the U.S. Geological Survey’s Hawaii Volcano Observatory and is republished by with permission.

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